SWITCHING POWER SUPPLY

摘要

PROBLEM TO BE SOLVED: To obtain a switching power supply wherein output voltage is controlled variably with an external signal by using a simple circuit constitution without needing the other power supply. SOLUTION: This switching power supply is provided with: a pulse-width modulation control circuit 70 for generating a pulse signal for pulse-width modulation controlling; a switching circuit 20 which makes output of a DC power supply intermittent according to a pulse signal from the pulse-width modulation control circuit 70 and generates a primary AC voltage; a rectification smoothing circuit 30 which rectifies and smooths a secondary AC voltage induced by application of the primary AC voltage generated with the switching circuit and generates DC voltage; and a voltage addition circuit 60 which adds an external signal EX input from outside to reference voltage Ref generated with the pulse-width modulation control circuit 70. The control circuit 70 generates a pulse signal having a pulse width corresponding to difference between DC voltage generated with the rectification smoothing circuit 30 and voltage output from the voltage addition circuit 60. COPYRIGHT: (C)2004,JPO&NCIPI